Apparatus and method

ABSTRACT

[Object] To provide a mechanism capable of more appropriately ascertaining an interference condition of a data signal. 
     [Solution] An apparatus includes: a processing unit that feeds back a channel quality indicator (CQI) of a serving base station, which is calculated on a basis of results of measuring reference signals received from the serving base station and a neighbor base station and information related to a power difference between the reference signal and a data signal of the neighbor base station, to the serving base station.

TECHNICAL FIELD

The present disclosure relates to apparatuses and methods.

BACKGROUND ART

In the Third Generation Partnership Project (3GPP), various techniquesfor improving the capacity of a cellular system are currently studied inorder to accommodate explosively increasing traffic. It is alsoenvisaged that the required capacity will become about 1000 times thecurrent capacity in the future. Techniques such as multi-usermulti-input multiple-input multiple-output (MU-MIMO), coordinatedmultipoint (CoMP), and the like could increase the capacity of acellular system by a factor of as low as less than ten. Therefore, thereis a demand for an innovative technique.

For example, as a technique for significantly increasing the capacity ofa cellular system, a base station may perform beamforming using adirectional antenna including a large number of antenna elements (e.g.,about 100 antenna elements). Such a technique is a kind of techniquecalled large-scale MIMO or massive MIMO. By such beamforming, thehalf-width of a beam is narrowed. In other words, a sharp beam isformed. Also, if the large number of antenna elements are arranged in aplane, a beam aimed in a desired three-dimensional direction can beformed.

For example, Patent Literatures 1 to 3 disclose techniques applied whena directional beam aimed in a three-dimensional direction is used.

CITATION LIST Patent Literature

Patent Literature 1: JP 2014-204305A

Patent Literature 2: JP 2014-53811A

Patent Literature 3: JP 2014-64294A

DISCLOSURE OF INVENTION Technical Problem

Measurement of a CQI in UE is performed mainly on the basis of a resultof measuring a received power of a reference signal. However, there is acase in which a difference occurs between the received power of thereference signal and the received power of a data signal. Thisdifference can similarly occur in a signal from a serving eNB and asignal from a neighbor eNB. Therefore, there is a case in which a CQIthat indicates an interference condition of the reference signal that isdifferent from an interference condition of the data signal is fed backto eNB.

Thus, it is desirable to provide a mechanism capable of moreappropriately ascertaining an interference condition of a data signal.

Solution to Problem

According to the present disclosure, there is provided an apparatusincluding: a processing unit that feeds back a channel quality indicator(CQI) of a serving base station, which is calculated on a basis ofresults of measuring reference signals received from the serving basestation and a neighbor base station and information related to a powerdifference between the reference signal and a data signal of theneighbor base station, to the serving base station.

In addition, according to the present disclosure, there is provided anapparatus including: a processing unit that provides a notification ofinformation related to a power difference between a reference signal anda data signal of a neighbor base station to a terminal apparatus underthe control of the apparatus and receives feedback of a CQI that iscalculated on a basis of results of measuring reference signals that arereceived from a serving base station and the neighbor base station andinformation related to the difference from the terminal apparatus.

In addition, according to the present disclosure, there is provided amethod including: feeding back a channel quality indicator (CQI) of aserving base station, which is calculated on a basis of results ofmeasuring reference signals received from the serving base station and aneighbor base station and information related to a power differencebetween the reference signal and a data signal of the neighbor basestation, to the serving base station.

Advantageous Effects of Invention

According to the present disclosure, a mechanism capable of moreappropriately ascertaining an interference condition of a data signal isprovided as described above. Note that the effects described above arenot necessarily limitative. With or in the place of the above effects,there may be achieved any one of the effects described in thisspecification or other effects that may be grasped from thisspecification.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram for describing a weight set for large-scale MIMObeamforming.

FIG. 2 is a diagram for describing an example of a case in whichbeamforming of large-scale MIMO is performed.

FIG. 3 is a diagram for describing a relationship between multiplicationof weight coefficients and insertion of a reference signal.

FIG. 4 is a diagram for describing a relationship between multiplicationby a weight coefficient and insertion of a reference signal in a newapproach.

FIG. 5 is a flowchart illustrating an example of a flow of CQIcalculation processing executed by UE of LTE in the related art.

FIG. 6 is a diagram for describing an example of a schematicconfiguration of a system according to an embodiment of the presentdisclosure.

FIG. 7 is a block diagram illustrating an example of a configuration ofa base station according to the present embodiment.

FIG. 8 is a block diagram illustrating an example of a configuration ofa terminal apparatus according to the present embodiment.

FIG. 9 is an explanatory diagram for explaining technical features of afirst embodiment.

FIG. 10 is an explanatory diagram for explaining technical features ofthe embodiment.

FIG. 11 is an explanatory diagram for explaining technical features ofthe embodiment.

FIG. 12 is an explanatory diagram for explaining technical features ofthe embodiment.

FIG. 13 is an explanatory diagram for explaining technical features of asecond embodiment.

FIG. 14 is an explanatory diagram for explaining technical features ofthe embodiment.

FIG. 15 is an explanatory diagram for explaining technical features ofthe embodiment.

FIG. 16 is an explanatory diagram for explaining technical features ofthe embodiment.

FIG. 17 is a block diagram illustrating a first example of a schematicconfiguration of an eNB.

FIG. 18 is a block diagram illustrating a second example of theschematic configuration of the eNB.

FIG. 19 is a block diagram illustrating an example of a schematicconfiguration of a smartphone.

FIG. 20 is a block diagram illustrating an example of a schematicconfiguration of a car navigation apparatus.

MODE(S) FOR CARRYING OUT THE INVENTION

Hereinafter, (a) preferred embodiment(s) of the present disclosure willbe described in detail with reference to the appended drawings. Notethat, in this specification and the appended drawings, structuralelements that have substantially the same function and structure aredenoted with the same reference numerals, and repeated explanation ofthese structural elements is omitted.

In addition, there are cases in the present specification and thediagrams in which constituent elements having substantially the samefunctional configuration are distinguished from each other by affixingdifferent letters to the same reference numbers. For example, aplurality of constituent elements having substantially the samefunctional configuration are distinguished, like neighbor base stations300A and 300B, if necessary. However, when there is no particular needto distinguish a plurality of constituent elements having substantiallythe same functional configuration from each other, only the samereference number is affixed thereto. For example, when there is noparticular need to distinguish neighbor base stations 300A and 300B,they are referred to simply as neighbor base stations 300.

Note that the description will be given in the following order.

1. Introduction

1.1. Related techniques

1.2. Consideration related to embodiment of the present disclosure

2. Configuration example

2.1. Schematic configuration example of system

2.2. Configuration example of base station

2.3. Configuration of terminal apparatus

3. First Embodiment

3.1. Technical problems

3.2. Technical features

4. Second Embodiment

4.1. Technical problems

4.2. Technical features

5. Application examples

6. Conclusion

1. Introduction

First of all, techniques related to an embodiment of the presentdisclosure and consideration related to the present embodiment will bedescribed with reference to FIGS. 1 to 5.

1.1. Related Techniques

Beamforming and measurement will be described as techniques related toan embodiment of the present disclosure with reference to FIGS. 1 to 4.

(1) Beamforming

(a) Necessity of Large-Scale MIMO

In the 3GPP, various techniques for improving the capacity of a cellularsystem are currently studied in order to accommodate explosivelyincreasing traffic. It is envisaged that the required capacity willbecome about 1000 times the current capacity in the future. Techniquessuch as MU-MIMO, CoMP, and the like could increase the capacity of acellular system by a factor of as low as less than ten. Therefore, thereis a demand for an innovative technique.

Release 10 of the 3GPP specifies that eNode B is equipped with eightantennas. Therefore, the antennas can provide eight-layer MIMO in thecase of single-user multi-input multiple-input multiple-output(SU-MIMO). Eight-layer MIMO is a technique of spatially multiplexingeight separate streams. Alternatively, the antennas can providefour-user two-layer MU-MIMO.

User equipment (UE) has only a small space for accommodating an antenna,and limited processing capability, and therefore, it is difficult toincrease the number of antenna elements in the antenna of UE. However,recent advances in antenna mounting technology have allowed eNnode B toaccommodate a directional antenna including about 100 antenna elements.

For example, as a technique for significantly increasing the capacity ofa cellular system, a base station may perform beamforming using adirectional antenna including a large number of antenna elements (e.g.,about 100 antenna elements). Such a technique is a kind of techniquecalled large-scale MIMO or massive MIMO. By such beamforming, thehalf-width of a beam is narrowed. In other words, a sharp beam isformed. Also, if the large number of antenna elements are arranged in aplane, a beam aimed in a desired three-dimensional direction can beformed. For example, it has been proposed that, by forming a beam aimedat a higher position than that of a base station (e.g., a higher floorof a high-rise building), a signal is transmitted to a terminalapparatus located at that position.

In typical beamforming, the direction of a beam can be changed in thehorizontal direction. Therefore, it can be said that the typicalbeamforming is two-dimensional beamforming. Meanwhile, in large-scaleMIMO (or massive MIMO) beamforming, the direction of a beam can bechanged in the vertical direction as well as the horizontal direction.Therefore, it can be said that large-scale MIMO beamforming isthree-dimensional beamforming.

Note that the increase in the number of antennas allows for an increasein the number of MU-MIMO users. Such a technique is another form of thetechnique called large-scale MIMO or massive MIMO. Note that when thenumber of antennas in UE is two, the number of spatially separatedstreams is two for a single piece of UE, and therefore, it is morereasonable to increase the number of MU-MIMO users than to increase thenumber of streams for a single piece of UE.

(b) Weight Set

A set of weight for beamforming are represented by a complex number(i.e., a set of weight coefficients for a plurality of antennaelements). An example of a weight set particularly for large-scale MIMObeamforming will now be described with reference to FIG. 1.

FIG. 1 is a diagram for describing a weight set for large-scale MIMObeamforming. FIG. 1 shows antenna elements arranged in a grid pattern.In addition, FIG. 1 also shows two orthogonal axes x and y in a plane inwhich the antenna elements are arranged, and an axis z perpendicular tothe plane. Here, the direction of a beam to be formed is, for example,represented by an angle phi (Greek letter) and an angle theta (Greekletter). The angle phi (Greek letter) is an angle between an xy-planecomponent of the direction of a beam and the x-axis. Also, the angletheta (Greek letter) is an angle between the beam direction and thez-axis. In this case, for example, the weight coefficient V_(m, n) of anantenna element which is m-th in the x-axis direction and n-th in they-axis direction is represented as follows.

$\begin{matrix}{{V_{m,n}\left( {\theta,\varphi,f} \right)} = {\exp\left( {j\; 2\pi\frac{f}{c}\left\{ {{\left( {m - 1} \right)d_{x}{\sin(\theta)}{\cos(\varphi)}} + {\left( {n - 1} \right)d_{y}{\sin(\theta)}{\sin(\varphi)}}} \right\}} \right)}} & \left\lbrack {{Math}.\mspace{14mu} 1} \right\rbrack\end{matrix}$

In formula (1), f is a frequency, and c is the speed of light. Also, jis the imaginary unit of a complex number. Also, d_(x) is an intervalbetween each antenna element in the x-axis direction, and d_(y) is aninterval between each antenna element in the y-axis direction. Note thatthe coordinates of an antenna element are represented as follows.x=(m−1)d, y=(n−1)d,  [Math. 2]

A weight set for typical beamforming (two-dimensional beamforming) maybe divided into a weight set for acquiring directivity in the horizontaldirection and a weight set for phase adjustment of dual layer MIMO(i.e., a weight set for phase adjustment between two antenna subarrayscorresponding to different polarized waves). On the other hand, a weightset for beamforming of large-scale MIMO (three-dimensional beamforming)may be divided into a first weight set for acquiring directivity in thehorizontal direction, a second weight set for acquiring directivity inthe vertical direction, and a third weight set for phase adjustment ofdual layer MIMO.

(c) Change in Environment Due to Large-Scale MIMO Beamforming

When large-scale MIMO beamforming is performed, the gain reaches 10 dBor more. In a cellular system employing the above beamforming, asignificant change in radio wave environment may occur compared to aconventional cellular system.

(d) Case where Large-Scale MIMO Beamforming is Performed

For example, a base station in urban areas may form a beam aimed at ahigh-rise building. Also, even in rural areas, a base station of a smallcell may form a beam aimed at an area around the base station. Note thatit is highly likely that a base station of a macro-cell in rural areasdoes not perform large-scale MIMO beamforming.

FIG. 2 is a diagram for describing an example of a case in whichbeamforming of large-scale MIMO is performed. Referring to FIG. 2, abase station 71 and a high-rise building 73 are illustrated. Forexample, the base station 71 forms a directional beam 79 toward thehigh-rise building 73 in addition to directional beams 75 and 77 towardthe ground.

(2) Measurement

Measurement includes measurement for selecting a cell and measurementfor feeding back a channel quality indicator (CQI) and the like afterconnection. The latter is required to be performed in a shorter time.Measurement of an amount of interference from a neighbor cell as well asmeasurement of quality of a serving cell may be considered as a kind ofsuch CQI measurement.

(a) CQI Measurement

Although a cell-specific reference signal (CRS) may be used for CQImeasurement, a channel state information reference signal (CSI-RS) hasmainly been used for CQI measurement since release 10.

A CSI-RS is transmitted without beamforming, similar to a CRS. That is,the CSI-RS is transmitted without being multiplied by a weight set forbeamforming, similar to a CRS. A specific example of this will bedescribed with reference to FIG. 3.

FIG. 3 is a diagram for describing the relationship betweenmultiplication of weight coefficients and insertion (or mapping) of areference signal. Referring to FIG. 3, a transmission signal 82corresponding to each antenna element 81 is complex-multiplied by aweight coefficient 83 by a multiplier 84. Thereafter, the transmissionsignal 82 complex-multiplied by the weight coefficient 83 is transmittedfrom the antenna element 81. Also, a demodulation reference signal(DM-RS) 85 is inserted before the multiplier 84, and iscomplex-multiplied by the weight coefficient 83 by the multiplier 84.Thereafter, the DM-RS 85 complex-multiplied by the weight coefficient 83is transmitted from the antenna element 81. Meanwhile, a CRS 86 (and aCSI-RS) is inserted after the multiplier 84. Thereafter, the CRS 86 (andthe CSI-RS) is transmitted from the antenna element 81 without beingmultiplied by the weight coefficient 83.

Since a CSI-RS is transmitted without beamforming as described above, apure channel (or a channel response H) which is not affected bybeamforming is estimated when measurement of the CSI-RS is performed.This channel H is used and a rank indicator (RI), a precoding matrixindicator (PMI) and a channel quality indicator (CQI) are fed back. Notethat only a CQI is fed back depending on a transmission mode. Also, anamount of interference may be fed back.

(b) CSI-RS

Since a CSI-RS is transmitted without beamforming before release 12 asdescribed above, the pure channel H which is not affected by beamformingis estimated when measurement of the CSI-RS is performed. Accordingly,the CSI-RS has been operated like a CRS.

A CRS is used for cell selection, synchronization and the like and thusa CRS transmission frequency is higher than a CSI-RS transmissionfrequency. That is, a CSI-RS period is longer than a CRS period.

There may be a first approach for transmitting a CSI-RS withoutbeamforming and a second approach for transmitting a CSI-RS withbeamforming (i.e., transmitting a CSI-RS over a directional beam) in alarge-scale MIMO environment. It can be said that the first approach isa conventional approach and the second approach is a new approach. Arelationship between multiplication by a weight coefficient andinsertion of a reference signal in the new approach (second approach)will be described below with reference to FIG. 4.

FIG. 4 is a diagram for describing relationship between multiplicationby a weight coefficient and insertion (or mapping) of a reference signalin the new approach. Referring to FIG. 4, a transmission signal 92corresponding to each antenna element 91 is complex-multiplied by aweight coefficient 93 by a multiplier 94. Thereafter, the transmissionsignal 92 complex-multiplied by the weight coefficient 93 is transmittedfrom the antenna element 91. Also, a DM-RS 95 is inserted before themultiplier 94, and is complex-multiplied by the weight coefficient 93 bythe multiplier 94. Thereafter, the DM-RS 95 complex-multiplied by theweight coefficient 93 is transmitted from the antenna element 91.Further, a CSI-RS 96 is inserted in front of the multiplier 94, and iscomplex-multiplied by the weight coefficient 93 in the multiplier 94.Then, the CSI-RS 96 complex-multiplied by the weight coefficient 93 istransmitted from the antenna element 91. Meanwhile, a CRS 97 (and anormal CSI-RS) is inserted after the multiplier 94. Thereafter, the CRS97 (and the normal CSI-RS) is transmitted from the antenna element 91without being multiplied by the weight coefficient 93.

1.2. Consideration Related to Embodiment of Present Disclosure

Consideration related to an embodiment of the present disclosure will bedescribed with reference to FIG. 5.

(1) CSI-RS

A CSI-RS is defined in release 10. A normal CSI-RS is also referred toas a non-zero-power CSI-RS. The purpose of the CSI-RS is to acquire apure channel and thus the CSI-RS is transmitted without beamforming.

Also, a zero-power CSI-RS is defined. The zero-power CSI-RS is definedin order to enable easy observation of relatively weak signals fromother eNBs. Since an eNB does not transmit a signal in radio resources(resource elements) for the zero-power CSI-RS, a UE can receive signalsfrom other eNBs in the radio resources. The zero-power CSI-RS is alsoreferred to as an interference measurement resource (IMR).

A CSI-RS period is variable between 5 ms and 80 ms. In addition, 400radio resources are prepared in one subframe as candidates for radioresources in which the CSI-RS is transmitted.

Conventionally, only one CSI-RS is configured for one cell. On the otherhand, a plurality of zero-power CSI-RSs can be configured for one cell.Accordingly, when a serving eNB of a UE configures a zero-power CSI-RSin accordance with a configuration of a CSI-RS of a neighbor eNB, the UEcan perform measurement of the CSI-RS of the neighbor eNB without beingaffected by a signal from the serving eNB.

Note that a CSI-RS configuration is cell-specific. A UE may be notifiedof the configuration through signaling of a higher layer.

The embodiment is based on the assumption that the approach oftransmitting the CSI-RS with beamforming, which has been described abovewith reference to FIG. 4, is employed. However, an approach oftransmitting the CSI-RS with no beamforming may also be employedaccording to the embodiment. That is, a case in which only the CSI-RSwith beamforming is transmitted and a case in which the CSI-RS withbeamforming and the CSI-RS with no beamforming are present together areassumed according to the embodiment.

(2) Necessity of Optimization of Beamforming

When only a desired directional beam arrives at a UE, the UE can obtainhigh received quality. On the other hand, when not only a desireddirectional beam but also other directional beams arrive at a UE,received quality of the UE may deteriorate. For example, an interferencecan occur between reflected beams, and reception quality can deterioratein an environment with a large number of reflected waves. In addition,an interference with beams from the neighbor eNB can occur, for example,and reception quality can deteriorate.

In order to suppress such interference, first of all, it is importantfor an eNB to ascertain a situation of interference of a directionalbeam. A UE reporting a situation of interference of a directional beamto the eNB is considered because the eNB cannot be aware of thesituation of such interference of the directional beam. For example,calculating an amount of interference of a directional beam other than adesired directional beam from a CSI-RS is considered. Also, use of a CSIfeedback procedure is considered.

In general, there are two types of channel quality measurement. One typeis radio resource management (RRM) measurement such as measurement ofreference signal received power (RSRP) and reference signal receivedquality (RSRQ) and the other is measurement for deciding an RI, a CQI, aPMI and the like included in CSI. The former is mainly performed forcell selection by both a UE in an RRC idle mode and a UE in an RRCconnected mode. On the other hand, the latter is performed to recognizean interference situation by a UE in an RRC connected mode.

(3) CQI

Settings related to the reference signal that the UE uses forcalculating the CQI is called a CSI-RS configuration. The CSI-RSconfiguration includes information that indicates the position and thecycle of the CSI-RS (the position of the CSI-RS in a resource block anda cycle of a sub-frame into which the CSI-RS is inserted) that areprovided by the serving eNB. The UE can ascertain the position and thecycle of the CSI-RS with reference to the CSI-RS configuration and canperform measurement and reporting using the CSI-RS. In this manner, theUE can receive a desired signal that has been transmitted from theserving eNB by using transmission settings suitable for itself.

For calculating the CQI, information about the received power of aninterference signal is also used as well as the received power of thedesired signal. Here, the interference signal is a signal that comesfrom the neighbor eNB. In order for the UE to be able to measure theinterference signal, a notification of the information that indicatesthe position and the cycle of the IMR for measuring the interferencesignal from the neighbor eNB is provided as an IMR configuration to theUE. The UE can ascertain the position and the cycle of the IMR withreference to the IMR configuration and can measure the interferencesignal. Then, the UE calculates the CQI by using the results ofmeasuring the desired signal and the interference signal. The IMRtypically receives the CSI-RS that comes from the neighbor eNB.

However, one IMR can measure one or more reference signals from one ormore neighbor eNBs. That is, it is difficult to identify from which beamfrom which neighbor eNB the interference comes and how large theinterference is, from the measurement result of the IMR. Therefore, themeasurement result of the IMR is used for measuring the total amount ofthe interference.

(4) First Estimation Error of Interference Power

In order for the UE to accurately calculate the CQI, it is important toaccurately estimate the power of the desired signal (optical signalpower) and the power of the interference signal (interference signalpower) on the basis of downlink channel information that has beenobtained by measuring the CSI-RS. In a case in which these values haveerrors, the CQI becomes not accurate, a modulation scheme is incorrectlyselected on the side of the eNB, and a decrease in a throughput canoccur, for example.

The point to be noted here is that the CSI-RS is a reference signal andis not a data signal. That is, a difference in received power can occurbetween the reference signal and the data signal. Therefore, it isdesirable that the UE estimate the received power of the desired datasignal (that is, the data signal from the serving eNB) and the receivedpower of the interference data signal (that is, the data signal from theneighbor eNB) and calculate the CQI on the basis of the estimationresult. Thus, the UE can estimate the received power of the desired datasignal on the basis of the result of measuring the CSI-RS from theserving eNB. In addition, the UE can estimate the received power of theinterference data signal by measuring the signal (typically, the CSI-RS)form the neighbor eNB with the IMR.

However, the result of estimating the received power of the desired datasignal and the interference data signal can include errors.

One of causes of the error included in the estimated received power ofthe desired data signal is that there is a difference between thereceived power of the CSI-RS from the serving eNB and the received powerof the physical downlink shared channel (PDSCH). According to the 3GPPstandard (3GPP TS 36.213), a parameter Pc is provided in the CSI-RSconfiguration in order for the UE to be able to estimate the receivedpower of the desired data signal in consideration of the difference. Theparameter Pc is an estimated ratio of energy per resource element (EPRE)of the PDSCH with respect to EPRE of the CSI-RS. The UE can ascertainthe power difference between the CSI-RS from the serving eNB and thePDSCH by acquiring the parameter Pc from the CSI-RS configuration andcan more accurately correct the received power of the desired datasignal. Hereinafter, an example of a flow of CQI calculation processingin the LTE in the related art will be described with reference to FIG.5.

FIG. 5 is a flowchart illustrating an example of a flow of CQIcalculation processing executed by the UE of the LTE in the related art.As illustrated in FIG. 5, the UE estimates the received power of thedesired data signal on the basis of the CSI-RS of the serving eNB (StepS102). Then, the UE corrects the error in the estimated received powerby using Pc of the serving eNB (Step S104). Meanwhile, the UE estimatesthe received power of the interference data signal on the basis of theCSI-RS of the neighbor eNB (Step S112). Then, the UE calculates the CQIon the basis of these estimation results (Step S120).

Here, the difference between the received power of the CSI-RS from theneighbor eNB and the received power of the PDSCH is exemplified as oneof the causes of the error in the estimated received power of theinterference data signal in a similar manner to the desired data signal.However, it is difficult for the UE to reduce the error in the estimatedreceived power of the interference data signal since a notification ofthe parameter Pc of the neighbor eNB is not provided.

Thus, a technique of providing Pc of the neighbor eNB to the UE will beprovided in the first embodiment.

(5) Second Error in Estimated Interference Power

The method of estimating the received power of the interference datasignal on the basis of the CSI-RS from the neighbor eNB has beendescribed above on the assumption that the data signal is transmittedfrom the neighbor eNB. However, there is also a case in which no datasignal is transmitted, and a large error in the estimation occurs sincethe interference power estimated on the basis of the CSI-RS does notactually come in such a case. In the large-scale MIMO system in which anantenna gain is larger than that of the LTE in the related art, whetheror not the data signal is transmitted (that is, whether the PDSCH isused or not used) greatly affects the error in the estimatedinterference power.

Thus, a technique capable of reducing the error in the estimation thatis caused depending on whether the PDSCH is used or not used byexchanging information related to transmission schedules of the PDSCHbetween eNBs will be provided in the second embodiment.

2. Configuration Example 2.1. Schematic Configuration Example of System

Next, a schematic configuration of a communication system 1 according toan embodiment of the present disclosure will be described with referenceto FIG. 6. FIG. 6 is a diagram for describing an example of theschematic configuration of the communication system 1 according to anembodiment of the present disclosure. Referring to FIG. 6, the system 1includes a base station 100, a terminal apparatus 200, and a neighborbase station 300. The system 1 is a system which complies with, forexample, LTE, LTE-Advanced, or similar communication standards.

(Base Station 100)

The base station 100 performs wireless communication with the terminalapparatuses 200. For example, the base station 100 performs wirelesscommunication with the terminal apparatuses 200 located in a cell 10 ofthe base station 100.

Particularly, in the embodiment, the base station 100 performsbeamforming. For example, the beamforming is beamforming of large-scaleMIMO. The beamforming may also be referred to as beamforming of massiveMIMO, beamforming of free dimension MIMO or three-dimensionalbeamforming. Specifically, for example, the base station 100 includes adirectional antenna usable for large-scale MIMO and performs beamformingof large-scale MIMO by multiplying a transmission signal by a weight setfor the directional antenna.

Further, the base station 100 can transmit the reference signal forchannel quality measurement by a directional beam, in particular, in theembodiment. It is a matter of course that the base station 100 maytransmit the reference signal without using the directional beam. Forexample, the reference signal is the CSI-RS. In addition, the basestation 100 can transmit the data signal by a directional beam. It is amatter of course that the base station 100 may transmit the data signalwithout using the directional beam. For example, the data signal is thePDSCH.

(Terminal Apparatus 200)

The terminal apparatus 200 performs wireless communication with a basestation. For example, the terminal apparatus 200 performs wirelesscommunication with the base station 100 when located within a cell 10 ofthe base station 100. For example, the terminal apparatus 200 performswireless communication with a neighbor base station 300 when locatedwithin a cell 30 of the neighbor base station 300.

(Neighbor Base Station 300)

The neighbor base station 300 is a neighbor base station of the basestation 100. For example, the neighbor base station 300 has a similarconfiguration to that of the base station 100 and performs similaroperations to those of the base station 100. Although FIG. 6 illustratestwo neighbor base stations 300, it is a matter of course that a singlebase station 300 may be included in the system 1, or three or more basestations 300 may be included in the system 1.

In the embodiment, the terminal apparatus 200 is assumed to be connectedto the base station 100. That is, the base station 100 is a serving basestation of the terminal apparatus 200, and the cell 10 is a serving cellof the terminal apparatus 200. The solid line arrow in the drawingrepresents the desired signal transmitted to the terminal apparatus 200,and the broken line arrow represents the interference signal.

Note that both the base station 100 and the neighbor base station 300may be base stations of macro cells. Alternatively, both the basestation 100 and the neighbor base station 300 may be base stations ofsmall cells. Alternatively, one of the base station 100 and the neighborbase station 300 may be a base station of a macro cell and the other ofthe base station 100 and the neighbor base station 300 may be a basestation of a small cell.

2.2. Configuration Example of Base Station

Next, an example of the configuration of the base station 100 accordingto an embodiment of the present disclosure will be described withreference to FIG. 7. FIG. 7 is a block diagram showing an example of theconfiguration of the base station 100 according to the embodiment of thepresent disclosure. Referring to FIG. 7, the base station 100 includesan antenna unit 110, a wireless communication unit 120, a networkcommunication unit 130, a storage unit 140, and a processing unit 150.

(Antenna Unit 110)

The antenna unit 110 radiates a signal output by the wirelesscommunication unit 120, in the form of radio waves, into space. Inaddition, the antenna unit 110 also converts radio waves in space into asignal, and outputs the signal to the wireless communication unit 120.

For example, the antenna unit 110 includes a directional antenna. Forexample, the directional antenna is a directional antenna which can beused in large-scale MIMO.

(Wireless Communication Unit 120)

The wireless communication unit 120 transmits and receives signals. Forexample, the wireless communication unit 120 transmits a downlink signalto the terminal apparatus 200 and receives an uplink signal from theterminal apparatus 200.

(Network Communication Unit 130)

The network communication unit 130 transmits and receives information.For example, the network communication unit 130 transmits information toother nodes and receives information from other nodes. For example, theother nodes include other base stations (for example, neighbor basestation 300) and a core network node.

(Storage Unit 140)

The storage unit 140 stores programs and data for operation of the basestation 100.

(Processing Unit 150)

The processing unit 150 provides various functions of the base station100. The processing unit 150 includes a setting unit 151 and acommunication control unit 153. Note that the processing unit 150 mayfurther include other components in addition to such components. Thatis, the processing unit 150 may perform operations other than operationsof such components.

Specific operations of the setting unit 151 and the communicationcontrol unit 153 will be described below in detail.

2.3. Configuration of Terminal Apparatus

Next, an example of the configuration of the terminal apparatus 200according to an embodiment of the present disclosure will be describedwith reference to FIG. 8. FIG. 8 is a block diagram for showing anexample of the configuration of the terminal apparatus 200 according tothe embodiment of the present disclosure. Referring to FIG. 8, theterminal apparatus 200 includes an antenna unit 210, a wirelesscommunication unit 220, a storage unit 230 and a processing unit 240.

(Antenna Unit 210)

The antenna unit 210 radiates a signal output by the wirelesscommunication unit 220, in the form of radio waves, into space. Inaddition, the antenna unit 210 also converts radio waves in space into asignal, and outputs the signal to the wireless communication unit 220.

(Wireless Communication Unit 220)

The wireless communication unit 220 transmits and receives signals. Forexample, the wireless communication unit 220 receives a downlink signalfrom the base station 100 and transmits an uplink signal to the basestation 100.

(Storage Unit 230)

The storage unit 230 stores a program and data for operation of theterminal apparatus 200.

(Processing Unit 240)

The processing unit 240 provides a variety of functions of the terminalapparatus 200. The processing unit 240 includes an acquisition unit 241and a measurement unit 243. Note that the processing unit 240 canfurther include components other than these components. That is, theprocessing unit 240 can perform operations other than the operations ofthese components.

Specific operations of the acquisition unit 241 and the measurement unit243 will be described later in detail.

3. First Embodiment

Hereinafter, a first embodiment will be described with reference toFIGS. 9 to 12.

3.1. Technical Problems

(1) First Problem

A technical problem of the embodiment is the error in the estimatedreceived power of the interference data signal that is caused by thedifference in the received power of the reference signal and the datasignal as described above. Therefore, a technology of providing anotification of a Pc of the neighbor base station 300 to the terminalapparatus 200 will be provided first in the embodiment.

(2) Second Problem

However, there is also a case in which it is difficult to reduce theerror in the estimated received power of the interference data signaleven if it becomes possible for the terminal apparatus 200 to acquirethe parameter Pc of the neighbor base station 300. This is because theparameter Pc can be received in a state in which CSI-RSs are presenttogether in a single IMR since the parameter Pc can be applied to thereceived power of the CSI-RSs corresponding to the parameter Pc.

In the LTE in the related art, such an error in the estimated receivedpower of the interference data signal that is caused by such a problemis not particularly considered as a problem. This is because the numberof antenna elements mounted on the eNB is small and the environment ofthe interference power does not greatly vary.

Meanwhile, since the environment of the interference power can greatlyvary in the large-scale MIMO, the error in the estimated received powerof the interference data signal can become a severe problem.

Specifically, a CSI-RS with beamforming and a CSI-RS with no beamformingare considered first in the large-scale MIMO. There are cases in whichthe PDSCH is subjected to the beamforming for each eNB in both schemes.In addition, the number of beams that are multiplexed at the same timechanges in some cases, and in such cases, the power of each beamchanges. In addition, a case in which an excessively large antenna gainis not used in order to avoid interference with the neighbor cell isalso assumed. As described above, the degree of freedom of the antennagain obtained by the beamforming can become larger in the environment ofthe large-scale MIMO as compared with the previous one.

Therefore, it is possible to state that there is a high likelihood thatthe degree of freedom in setting the parameter Pc for each CSI-RSconfiguration will be significantly greater than that in the previousone (specifically, 1 dB steps from −8 dB to 15 dB). In a case in whichthe degree of freedom in setting a Pc is significantly large, it isdifficult to reduce the error in the estimation by using a plurality ofPcs that are set with a high degree of freedom in the settings relatedto results of measuring a plurality of CSI-RSs from a single neighboreNB with a single IMR. Similar difficulty also occurs in a case in whicha plurality of CSI-RSs from a plurality of neighbor eNBs are presenttogether in a single IMR.

A method of restricting the degree of freedom in setting a Pc may beconsidered as an example of methods for solving this problem. In a casein which the degree of freedom in setting a Pc is restricted, it isconsidered to be possible to reduce the error in the estimated receivedpower of the interference data signal on the basis of the result ofmeasuring the IMR. However, if the degree of freedom in setting a Pc isrestricted, there is a possibility that interference due to unnecessaryradiation may occur or the number of UEs that can perform MU-MIMO byusing spatial multiplexing will be restricted.

Setting an IMR for each CSI-RS may be exemplified as another example ofthe methods for solving the problem. However, overheads of the IMR thatoccupies the wireless resource becomes excessively large in the method.In an environment in which small base stations are densely arranged, forexample, it is assumed that a large number of neighbor base stations asinterference sources are present in the neighborhood of the serving basestation. In addition, the number of types (directions, for example) ofthe beams that can be provided by a single base station is significantlylarge in the case of the large-scale MIMO. Therefore, the number of IMRsthat are set for measuring the CSI-RSs with beamforming from theneighbor base stations can become huge in a case in which the CSI-RSsare provided with beam forming.

Thus, a technique of more finely measuring the interference from theneighbor eNB by using a plurality of IMRs in accordance with the settingof a Pc will be further provided in the embodiment.

3.2. Technical Features

(1) Estimation Based on Pc of Neighbor Base Station

The base station 100 (for example, the setting unit 151) provides anotification of information related to a power difference between theCSI-RS of the neighbor base station 300 and the PDSC (that is, theinformation related to the parameter Pc) to the terminal apparatus 200.In this manner, the terminal apparatus 200 (for example, the acquisitionunit 241) acquires the information related to the power differencebetween the CSI-RS of the neighbor base station 300 and the PDSCH (thatis, Pc). This station is included in the IMR configuration, for example,and the notification thereof is provided from the base station 100 tothe terminal apparatus 200. That is, the IMR configuration includes theinformation related to a Pc in addition to the information thatindicates the position and the cycle of the IMR.

The terminal apparatus 200 (for example, the measurement unit 243)measures the CSI-RSs received from the base station 100 and the neighborbase stations 300. Then, the terminal apparatus 200 (for example, themeasurement unit 243) calculates the CQI of the neighbor base station300 on the basis of the results of measuring the CSI-RSs and the IMRconfiguration and feeds back the CQI to the base station 100. Here, theterminal apparatus 200 (measurement unit 243) estimates the receivedpower of the interference data signal on the basis of the IMRconfiguration and then calculates the CQI. Since the CQI based on thereceived power of the interference data signal with a reduced error inthe estimation is fed back, the base station 100 (for example, thecommunication control unit 153) can select an appropriate modulationscheme, for example.

(2) Grouping of Interference Signals

In the embodiment, reference signals (the CSI-RSs of neighbor basestations 300) are grouped in accordance with Pc. Then, the referencesignals are received by an IMR corresponding to a group (that is,corresponding to Pc of the reference signals). Referring to FIG. 9,specific description will be given of this point.

As illustrated in FIG. 9, a plurality of IMRs 42 are set for a wirelessresource (typically, a resource block) 40. Pc is set for each IMR 42,and a CSI-RS with the set Pc arrives the IMR 42. For example, a CSI-RSwith Pc of −10 dB is received by the IMR 42A. A CSI-RS with Pc of 0 dBis received by the IMR 42B. A CSI-RS with Pc of 10 dB is received by theIMR 42C. A CSI-RS with Pc of 20 dB is received by the IMR 42D.

The terminal apparatus 200 (for example, the measurement unit 243)estimates the received power of the interference data signal on thebasis of the received power that is measured by each IMR 42. It is amatter of course that one or more CSI-RSs can be present and receivedtogether by each IMR 42. In that case, it is difficult to estimate thereceived power of the interference data signals corresponding to theindividual CSI-RSs. Therefore, the received power that is estimated bythe terminal apparatus 200 is an approximate value of the received powerwith large interference among the interference data signals.

The IMR configuration, the notification of which is provided from thebase station 100 to the terminal apparatus 200, includes the informationthat indicates Pc corresponding to each IMR. In this manner, theterminal apparatus 200 can ascertain the CSI-RS with which Pc is toarrive which IMR and can estimate the approximate values of the receivedpower of the interference data signals.

The base station 100 (for example, the setting unit 151) sets theposition of the IMR and also sets Pc corresponding to the IMR. Note thatthe setting can be performed on the basis of an instruction from anoperator who uses an operation and maintenance (O & M) interface.

It is desirable that the information related to the position of the IMRand corresponding Pc be shared between the base station 100 and theneighbor base station 300 in order to cause the CSI-RS withcorresponding Pc to arrive the IMR. Hereinafter, an example of a sharingmethod will be described. Note that the information related to the IMR,which is exchanged between the base station 100 and the neighbor basestation 300, is also referred to as IMR assignment information below.

First Example

A first example is a mode in which the position of the IMR and Pccorresponding to the IMR of each base station are decided by theoperator, and notifications thereof is provided to each base station.According to the example, the neighbor base stations 300 can transmitthe CSI-RS so as to be received by the IMR with corresponding Pc fromamong the IMRs of the base station 100 since the position of the IMR ofthe base station 100 and Pc are ascertained by the neighbor base station300. In this manner, the CSI-RSs of the neighbor base stations 300 canbe received by the IMRs corresponding to Pc of the CSI-RSs.

In this example, it is not necessary to exchange the information betweenthe base station 100 and the neighbor base station 300.

Second Example

A second example is a mode in which a rule related to the position ofthe IMR of each base station and Pc (hereinafter, referred to as agrouping rule) is decided by the operator, and each base station decidesthe position of the IMR and Pc corresponding to the IMR. For example,the grouping rule can include information that indicates a roughposition of IMRs, reference levels of the Pc to be set, the upper limitnumber of IMRs, and the like.

In this example, the base station 100 provides a notification of the IMRassignment information to the neighbor base stations 300. The IMRassignment information includes information that indicates the positionsof the IMR. In addition, the IMR assignment information includesinformation that indicates Pc corresponding to each IMR in the basestation 100. The neighbor base station 300 transmits the CSI-RS so as tobe received by the IMR with corresponding Pc among the IMRs of the basestation 100 on the basis of the IMR assignment information. In thismanner, the CSI-RSs of the neighbor base stations 300 can be received bythe IMRs corresponding to the Pc of the CSI-RSs. Note that thenotification of the information that is common to the base station 100and the neighbor base station 300 in the IMR assignment information maybe omitted. In a case in which the positions, and the numbers of theIMRs, setting of corresponding Pc, and the like are common to the basestation 100 and the neighbor base stations 300, for example, thenotification itself of the IMR assignment information may be omitted.

Third Example

A third example is similar to the second example in that the groupingrule is decided by the operator. As a different point, this example is amode in which the base station 100 decides the position of the IMR andPc corresponding to the IMR on the basis of the information about theCSI-RS that is transmitted from the neighbor base station 300.

In this example, the neighbor base station 300 provides the notificationof the IMR assignment information to the base station 100. The IMRassignment information includes information that indicates a schedule (afrequency, a time, a beam, and the like) in which the CSI-RS istransmitted. In addition, the IMR assignment information includes theinformation that indicates the Pc corresponding to the CSI-RS. The basestation 100 (for example, the setting unit 151) sets the IMR and setsthe Pc on the basis of the acquired IMR assignment information. In thismanner, the CSI-RS of the neighbor base station 300 can be received bythe IMR corresponding to the Pc of the CSI-RS. Note that thenotification of the information that is common to the base station 100and the neighbor base station 300 in the IMR assignment information maybe omitted.

Flow of Processing

Hereinafter, examples of flows of processing calculating the CQI by theterminal apparatus 200 according to the embodiment and processing of theentire system 1 will be described with reference to FIGS. 10 and 11.

FIG. 10 is a flowchart illustrating an example of a flow of processingcalculating the CQI that is executed by the terminal apparatus 200according to the embodiment. As illustrated in FIG. 10, the terminalapparatus 200 (for example, the measurement unit 243) estimates receivedpower of a desired data signal on the basis of the CSI-RS of the basestation 100 (Step S102). Then, the terminal apparatus 200 (for example,the measurement unit 243) corrects an error in estimated received powerby using Pc of the base station 100 (Step S104). Meanwhile, the terminalapparatus 200 (for example, the measurement unit 243) estimates receivedpower of the interference data signal on the basis of the CSI-RS of theneighbor base station 300 (Step S112). Next, the terminal apparatus 200(for example, the measurement unit 243) corrects the received power byusing the Pc of the neighbor base station 300 (Step S114). Then, theterminal apparatus 200 (for example, the measurement unit 243)calculates the CQI on the basis of these estimation results (Step S120).

FIG. 11 is a sequence diagram illustrating an example of a flow ofmeasurement report processing that is executed in the system 1 accordingto the embodiment. This sequence is a sequence related to theaforementioned second example. As illustrated in FIG. 11, the basestation 100 and the neighbor base station 300 acquires the grouping rulefrom the operator first (Step S202). The grouping rule includes, forexample, a reference of a level of the Pc to be set, the upper limitnumber of the IMRs, and the like. The base station 100 transmits aCSI-RS configuration to the terminal apparatus 200 (Step S204). Inaddition, the base station 100 transmits the IMR configuration to theterminal apparatus 200 (Step S206). Note that the IMR configuration maybe transmitted at the same time as the CSI-RS configuration (while beingincluded in the CSI-RS configuration, for example). Next, the basestation 100 provides the notification of the IMR assignment informationto the neighbor base station 300 (Step S208). Next, the base station 100transmits the CSI-RS to the terminal apparatus 200 (Step S210). Inaddition, the neighbor base station 300 transmits the CSI-RS to theterminal apparatus 200 so as to arrive the IMR with the corresponding Pcset by the terminal apparatus 200, with reference to the IMR assignmentinformation (Step S212). Then, the terminal apparatus 200 calculates theCQI as described above with reference to FIG. 10 (Step S214) and feedsback the CQI to the base station 100 (Step S216).

(3) Variations

Variations of the technique related to the grouping are considered in avariety of ways. Hereinafter, an example thereof will be described.

For example, CSI-RSs may be grouped for each neighbor base station 300.According to the grouping, the CSI-RSs of the neighbor base station 300are received by IMRs that are different for each neighbor base station300. In this manner, the terminal apparatus 200 can measure themagnitude of the interference for each neighbor base station 300 andrequest suppression of the interference for each neighbor base station300. In this case, the IMR configuration includes information thatindicates the neighbor base station 300 corresponding to each IMR. Inaddition, the IMR assignment information in the second example describedabove includes information that indicates the neighbor base station 300corresponding to each IMR of the base station 100.

For example, the IMR configuration may include information thatindicates a Pc corresponding to at least a part of IMRs. That is, theinformation that indicates the PC corresponding to a part of IMRs may beomitted. For an IMR with a Pc of 0 d B or a vicinity value, for example,the information that indicates the Pc may be omitted. This is becausethe error in the estimation is small in the first place. This omissionenables reduction of the amount of communication for providing thenotification of the IMR configuration.

For example, the base station 100 (for example, the setting unit 151)may control whether or not to provide the notification of theinformation that indicates the Pc corresponding to each IMR to theterminal apparatus 200 for each terminal apparatus 200. The desiredsignal is more dominant than the interference signal in relation to theterminal apparatus 200 that is located near the base station 100, forexample. Therefore, since whether or not to correct the error in theestimation by using the Pc has less influences on the SINR and the CQI,the notification and the correction of the error in the estimation maybe omitted. Specifically, the base station 100 (for example, the settingunit 151) may omit the notification in a case in which the sum of theentire interference power measured in all the IMRs set for the terminalapparatus 200 is equal to or less than a threshold value (about −110 dB,for example). In this case, the information that indicates the sum ofthe interference power is fed back from the terminal apparatus 200 tothe base station 100. The information that indicates the sum of theinterference power may be an index of 10 if the interference power is−100 dBm or an index of 9 if the interference power is −90 dBm, forexample. Hereinafter, an example of a flow of the processing will bedescribed with reference to FIG. 12.

FIG. 12 is a sequence diagram illustrating an example of a flow ofprocessing of determining whether or not to provide a notification ofthe information that indicates a Pc corresponding to each IMR that isexecuted in the system 1 according to the embodiment. As illustrated inFIG. 12, the base station 100 transmits the CSI-RS configuration to theterminal apparatus 200 (Step S302) and transmits the CSI-RS to theterminal apparatus 200 (Step S304). Next, the base station 100 transmitsa part of the IMR configuration (the information that indicates a Pccorresponding to the IMR is excluded; for example, the information thatindicates the position and the cycle of the IMR is included) to theterminal apparatus 200 (Step S306). Next, the terminal apparatus 200calculates the sum of the interference power (Step S308) and transmitsan index of the sum of the interference power to the base station 100(Step S310). Then, the base station 100 determines whether or not theinterference from the neighbor base station 300 is problematic, on thebasis of whether or not the sum of the interference power indicated bythe index is equal to or less than the threshold value, for example(Step S312). In a case in which it is determined that the interferenceis problematic (in a case in which the sum exceeds the threshold value,for example), the base station 100 provides a notification of a messageof an instruction for correcting the error in the estimation by usingthe Pc to the terminal apparatus 200 (Step S314). This message includesthe information that indicates the Pc corresponding to the IMR.Meanwhile, in a case in which it is determined that the interference isnot problematic (in a case in which the sum is equal to or less than thethreshold value, for example), the base station 100 omits thenotification of the message of the instruction for correcting theerroring the estimation by using the Pc.

Note that these variations may be appropriately combined. For example,the CSI-RSs may be grouped for each neighbor base station 300 for theneighbor base stations 300 near the terminal apparatus 200, and thecorrection of the error in the estimation may be omitted for theneighbor base stations 300 far from the terminal apparatus 200.

4. Second Embodiment

Next, a second embodiment will be described with reference to FIGS. 13to 16.

4.1. Technical Problems

Whether or not the PDSCH is actually used greatly affects the amount ofinterference. In the first embodiment, the received power of theinterference data signal is estimated on the assumption that the datasignal is transmitted from the neighbor base station 300. Therefore, alarge error in the estimation can occur in the estimation methodaccording to the first embodiment in a case in which the data signal isnot transmitted from the neighbor base station 300.

Here, if the schedule information related to the frequency, the time,the beam, and the like of the PDSCH transmitted from the neighbor basestation 300 is ascertained, it is considered to be possible to correctthis error in the estimation. However, since the downlink assignmentcorresponding to the schedule information in the LTE in the related arthas a large amount of information and instantaneously provides anotification of the most recent schedule to the terminal apparatus undercontrol, the downlink assignment is not suitable for the purpose ofsharing the information with other base stations. In addition, althougha method of correcting the estimated value of the interference power onthe basis of the schedule information from the neighbor base station 300on the side of the base station 100 is also considered, overhead ofuplink communication for feeding back the estimated value of theinterference power is problematic in this method.

4.2. Technical Features

(1) Use of Schedule Information

In the embodiment, schedule information that indicates a roughtransmission schedule with reduced granularity as compared with that inthe related art. More specifically, the schedule information accordingto the embodiment is information that indicates restriction of atransmission schedule of the data signal in the neighbor base station300 in a predetermined period of time in the future. The restriction ofthe transmission schedule in the predetermined period of time in thefuture can also be stated as prediction of the transmission schedule.

A method of reducing the granularity in a frequency direction isexemplified as the method of reducing the granularity while the UE to beused is scheduled for each resource block that includes twelvesub-carriers and seven OFDM symbols in the LTE in the related art, forexample. For example, the schedule information may include informationthat indicates whether or not each sub-band is used for transmitting thedata signal. The sub-band can also be understood as a frequency bandthat includes a plurality of sub-carriers or a frequency band that isobtained by dividing a component carrier to a plurality of parts. Inaddition, the schedule information may include information thatindicates whether or not each beam is used to transmit the data signal.Note that the information that indicates whether or not the sub-band isused to transmit the data signal can also be understood as informationthat indicates a sub-band that is used with a high possibility. The sameapplies to beams.

The base station 100 (for example, the setting unit 151) acquires theschedule information (that is, the aforementioned information thatindicates the rough transmission schedule) in the neighbor base station300. Then, the base station 100 (for example, the setting unit 151)provides a notification of the acquired schedule information to theterminal apparatus 200. The schedule information may be included in theIMR configuration.

The terminal apparatus 200 (for example, the acquisition unit 241)acquires the schedule information from the base station 100. Then, theterminal apparatus 200 (for example, the measurement unit 243) furtherestimates received power of the interference data signal for eachsub-band on the basis of the schedule information. Specifically, theterminal apparatus 200 performs the estimation by the method describedin the first embodiment for the sub-band to be used and performs theestimation on the assumption that the received power is zero or a smallvalue for the sub-band that is not used. Then, the terminal apparatus200 calculates the CQI for each sub-band and feeds back the CQI. Anexample of the schedule information is illustrated in FIG. 13. Asillustrated in FIG. 13, the schedule information includes informationthat indicates whether or not each interference beam (the PDSCH withbeamforming) is used for each sub-band. For example, the terminalapparatus 200 calculates the CQI of the entire bandwidth (for example,the width of 20 MHz) in consideration only of N sub-bands that are usedwith a high possibility among M sub-bands as the interference power inrelation to an interference beam #1. If description is given whilefocusing on a sub-band #3, the terminal apparatus 200 separatelymeasures interference power of four interference beams (CSI-RS withbeamforming) by using four IMRs, then refers to the schedule informationfor each sub-band, and calculates the CQI in consideration only of theinterference power of the interference beams #2, #3, and #4.

Hereinafter, an example of a flow of processing calculating the CQI bythe terminal apparatus 200 according to the embodiment will be describedwith reference to FIG. 14.

FIG. 14 is a flowchart illustrating an example of a flow of processingof calculating the CQI1 that is executed in the terminal apparatus 200according to the embodiment. Processing related to Steps S102 to S114 isas described above with reference to FIG. 10. After Step S114, theterminal apparatus 200 (for example, the measurement unit 243) correctsthe error in estimated received power by using the schedule informationof the neighbor base station 300 (Step S116). Then, the terminalapparatus 200 (measurement unit 243) calculates the CQI on the basis ofthese estimation results (Step S120).

(2) Limitation of Sub-Band to Transmit CSI-RS

The LTE is typically run by a component carrier with a bandwidth of 20MHz, and the CQI is fed back in units of sub-bands obtained by dividing20 MHz into M parts. Following this procedure, the terminal apparatus200 (for example, the measurement unit 243) according to the embodimentmay calculate and feed back the CQI for each sub-band. The terminalapparatus 200 can also feed back a more accurate CQI for each sub-bandin this case by estimating the received power of the interference datasignal on the basis of the schedule information.

According to the LTE in the related art, one CSI-RS with beamforming istransmitted by all resource blocks with the bandwidth (for example, 20MHz). Meanwhile, the neighbor base station 300 may transmit the CSI-RSonly with the sub-band that is used with a high possibility for the datasignal to any of the terminal apparatuses 200. In this case, theterminal apparatus 200 under the control of the base station 100 canestimate the received power of the interference data signal inconsideration only of the sub-band that is used with a high possibilitywithout selecting the sub-band to be considered for estimating theinterference power on the basis of the schedule information. Inaddition, it is possible to reduce the resource for transmitting theCSI-RS and to reduce the IMR set by the base station 100 by limiting thesub-band in which the neighbor base station 300 transmits the CSI-RS toa part of the bandwidth. This is because only a smaller number of IMRsare necessary in the case in which the CSI-RS is transmitted only in apart of the bandwidth than in the case in which the CSI-RS istransmitted in the entire bandwidth.

The base station 100 shares the schedule information with the neighborbase station 300 and provides a notification of the shared scheduleinformation to the terminal apparatus 200. If this is more simplystated, the base station 100 provides a notification of the informationthat indicates the sub-band that is used with a high possibility, whichis shared with the neighbor base station 300, to the terminal apparatus200. In this manner, the terminal apparatus 200 can reduce processingburden by performing the measurement only in the sub-band of thenotification. The terminal apparatus 200 can estimate the received powerof the interference data signal in consideration only of the sub-bandthat is used with a high possibility as described above even in a casein which the notification of the schedule information is not provided tothe terminal apparatus 200. This is because the CSR-RS is transmittedonly in the sub band that is used with a high possibility from theneighbor base station 300.

Hereinafter, an example of a flow of processing in the entire system 1according to the embodiment will be described with reference to FIG. 15.

FIG. 15 is a sequence diagram illustrating an example of a flow ofmeasurement report processing that is executed in the system 1 accordingto the embodiment. Processing related to Steps S402 to S406 is similarto the processing related to Steps S202 to S206 described above withreference to FIG. 11. Next, the base station 100 and the neighbor basestation 300 mutually provide notifications of the schedule information(that is, the information that indicates the sub-band that is used withhigh possibility) (Step S408). Next, the base station 100 provides anotification of the schedule information to the terminal apparatus 200(Step S410). These notification of the schedules may be omitted. Next,the base station 100 transmits the CSI-RS to the terminal apparatus 200(Step S412). In addition, the neighbor base station 300 transmits theCSI-RS to the terminal apparatus 200 in the sub-band that is used with ahigh possibility with reference to the schedule information (Step S414).Then, the terminal apparatus 200 calculates the CQI as described abovewith reference to FIG. 14 (Step S416) and feeds back the CQI to the basestation 100 (Step S418).

(3) Setting of IMR Corresponding to Schedule Information

CSI-RSs of neighbor base stations 300 may be grouped in accordance withthe schedule information. In this manner, the CSI-RS of the neighborbase stations 300 are received by the IMRs of the groups correspondingto the schedule information of the neighbor base stations 300.

According to the embodiment, the notification of the scheduleinformation corresponding to each IMR is provided to the terminalapparatus 200. This information may be included in the IMRconfiguration. The terminal apparatus 200 can ascertain which IMR theCSI-RS under the control of which transmission schedule will arrive, bythe information. An example of the schedule information is illustratedin FIG. 16. As illustrated in FIG. 16, the schedule information includesinformation that indicates whether or not each sub-band is used for eachscheduling group (a group of the same or similar schedule information,for example). For example, a scheduling group #1 is a group for whichonly the sub-bands #2 and #4 are used. In addition, a scheduling group#2 is a group for which only the sub-bands #3 and # M are used. Ifdescription will be given while focusing on the sub-band #3, theterminal apparatus 200 separately measures the interference power of theCSI-RSs from the neighbor base stations 300 that belong to the fourgroups by using four IMRs and the calculates the CQI in considerationonly of the interference power of the scheduling groups #2, #3, and #4.

A flow of processing in a case in which IMRs corresponding to theschedule information may be similar to that described above withreference to FIG. 15. In such a case, the notification of the scheduleinformation corresponding to each IMR is provided to the terminalapparatus 200 in Step S410, for example.

5. Application Examples

The technique according to the present disclosure is applicable tovarious products. The base station 100 may also be implemented, forexample, as any type of evolved Node B (eNB) such as macro eNBs andsmall eNBs. Small eNBs may cover smaller cells than the macro cells ofpico eNBs, micro eNBs, home (femt) eNBs, or the like. Instead, the basestation 100 may be implemented as another type of base station such asNodes B, base transceiver stations (BTSs), or the like. The base station100 may include the main apparatus (which is also referred to as basestation apparatus) that controls wireless communication and one or moreremote radio heads (RRHs) that are disposed at different locations fromthat of the main apparatus. Also, various types of terminals describedbelow may function as the base station 100 by temporarily orsemi-permanently executing the functionality of the base station.Furthermore, at least some of components of the base station 100 may berealized in a base station apparatus or a module for a base stationapparatus.

Further, for example, the terminal apparatus 200 may be implemented as amobile terminal such as smartphones, tablet personal computers (PCs),notebook PCs, portable game terminals, portable/dongle mobile routers,and digital cameras, or an in-vehicle terminal such as car navigationapparatuses. In addition, the terminal apparatus 200 may be implementedas a machine type communication (MTC) for establishing a machine tomachine communication (M2M). Furthermore, at least some of components ofthe terminal apparatus 200 may be implemented as a module (e.g.integrated circuit module constituted with a single die) that is mountedon these terminals.

5.1. Application Examples for Base Station First Application Example

FIG. 17 is a block diagram illustrating a first example of a schematicconfiguration of an eNB to which the technology according to the presentdisclosure may be applied. An eNB 800 includes one or more antennas 810and a base station apparatus 820. Each antenna 810 and the base stationapparatus 820 may be connected to each other via an RF cable.

Each of the antennas 810 includes a single or a plurality of antennaelements (e.g. a plurality of antenna elements constituting a MIMOantenna) and is used for the base station apparatus 820 to transmit andreceive a wireless signal. The eNB 800 may include the plurality of theantennas 810 as illustrated in FIG. 17, and the plurality of antennas810 may, for example, correspond to a plurality of frequency bands usedby the eNB 800. It should be noted that while FIG. 17 illustrates anexample in which the eNB 800 includes the plurality of antennas 810, theeNB 800 may include the single antenna 810.

The base station apparatus 820 includes a controller 821, a memory 822,a network interface 823, and a wireless communication interface 825.

The controller 821 may be, for example, a CPU or a DSP, and operatesvarious functions of an upper layer of the base station apparatus 820.For example, the controller 821 generates a data packet from data in asignal processed by the wireless communication interface 825, andtransfers the generated packet via the network interface 823. Thecontroller 821 may generate a bundled packet by bundling data from aplurality of base band processors to transfer the generated bundledpacket. In addition, the controller 821 may also have a logical functionof performing control such as radio resource control, radio bearercontrol, mobility management, admission control, and scheduling. Thecontrol may be performed in cooperation with a surrounding eNB or a corenetwork. In addition, the memory 822 includes a RAM and a ROM, andstores a program executed by the controller 821 and a variety of controldata (such as, for example, terminal list, transmission power data, andscheduling data).

The network interface 823 is a communication interface for connectingthe base station apparatus 820 to the core network 824. The controller821 may communicate with a core network node or another eNB via thenetwork interface 823. In this case, the eNB 800 may be connected to acore network node or another eNB through a logical interface (e.g. S1interface or X2 interface). The network interface 823 may be a wiredcommunication interface or a wireless communication interface forwireless backhaul. When the network interface 823 is a wirelesscommunication interface, the network interface 823 may use a higherfrequency band for wireless communication than a frequency band used bythe wireless communication interface 825.

The wireless communication interface 825 supports a cellularcommunication system such as long term evolution (LTE) or LTE-Advanced,and provides wireless connection to a terminal located within the cellof the eNB 800 via the antenna 810. The wireless communication interface825 may typically include a base band (BB) processor 826, an RF circuit827, and the like. The BB processor 826 may, for example, performencoding/decoding, modulation/demodulation, multiplexing/demultiplexing,and the like, and performs a variety of signal processing on each layer(e.g. L1, medium access control (MAC), radio link control (RLC), andpacket data convergence protocol (PDCP)). The BB processor 826 may havepart or all of the logical functions as described above instead of thecontroller 821. The BB processor 826 may be a module including a memoryhaving a communication control program stored therein, a processor toexecute the program, and a related circuit, and the function of the BBprocessor 826 may be changeable by updating the program. In addition,the module may be a card or blade to be inserted into a slot of the basestation apparatus 820, or a chip mounted on the card or the blade.Meanwhile, the RF circuit 827 may include a mixer, a filter, anamplifier, and the like, and transmits and receives a wireless signalvia the antenna 810.

The wireless communication interface 825 may include a plurality of theBB processors 826 as illustrated in FIG. 17, and the plurality of BBprocessors 826 may, for example, correspond to a plurality of frequencybands used by the eNB 800. In addition, the wireless communicationinterface 825 may also include a plurality of the RF circuits 827, asillustrated in FIG. 17, and the plurality of RF circuits 827 may, forexample, correspond to a plurality of antenna elements. Note that, FIG.17 illustrates an example in which the wireless communication interface825 includes the plurality of BB processors 826 and the plurality of RFcircuits 827, but the wireless communication interface 825 may includethe single BB processor 826 or the single RF circuit 827.

In the eNB 800 illustrated in FIG. 17, one or more components includedin the processing unit 150 (the setting unit 151 and/or thecommunication control unit 153) described above with reference to FIG. 7may be mounted in the wireless communication interface 825.Alternatively, at least some of the components may be mounted in thecontroller 821. As an example, the eNB 800 may be equipped with a moduleincluding some or all components of the wireless communication interface825 (for example, the BB processor 826) and/or the controller 821, andthe above-described one or more components may be mounted in the module.In this case, the module may store a program causing the processor tofunction as the above-described one or more components (that is, aprogram causing the processor to perform the operation of theabove-described one or more components) and execute the program. Asanother example, the program causing the processor to function as theabove-described one or more components may be installed in the eNB 800,and the wireless communication interface 825 (for example, the BBprocessor 826) and/or the controller 821 may execute the program. Asdescribed above, the eNB 800, the base station apparatus 820, or themodule may be provided as an apparatus including the above-described oneor more components, and the program causing the processor to function asthe above-described one or more components may be provided. In addition,a readable recording medium in which the program is recorded may beprovided.

In addition, in the eNB 800 shown in FIG. 17, the wireless communicationunit 120 described with reference to FIG. 7 may be implemented by thewireless communication interface 825 (for example, the RF circuit 827).Moreover, the antenna unit 110 may be implemented by the antenna 810. Inaddition, the network communication unit 130 may be implemented by thecontroller 821 and/or the network interface 823. In addition, thestorage unit 140 may be implemented by the memory 822.

Second Application Example

FIG. 18 is a block diagram illustrating a second example of a schematicconfiguration of an eNB to which the technology according to the presentdisclosure may be applied. An eNB 830 includes one or more antennas 840,a base station apparatus 850, and an RRH 860. Each of the antennas 840and the RRH 860 may be connected to each other via an RF cable. Inaddition, the base station apparatus 850 and the RRH 860 may beconnected to each other by a high speed line such as optical fibercables.

Each of the antennas 840 includes a single or a plurality of antennaelements (e.g. plurality of antenna elements constituting a MIMOantenna), and is used for the RRH 860 to transmit and receive a wirelesssignal. The eNB 830 may include a plurality of the antennas 840 asillustrated in FIG. 18, and the plurality of antennas 840 may, forexample, correspond to a plurality of frequency bands used by the eNB830. Note that, FIG. 18 illustrates an example in which the eNB 830includes the plurality of antennas 840, but the eNB 830 may include thesingle antenna 840.

The base station apparatus 850 includes a controller 851, a memory 852,a network interface 853, a wireless communication interface 855, and aconnection interface 857. The controller 851, the memory 852, and thenetwork interface 853 are similar to the controller 821, the memory 822,and the network interface 823 described with reference to FIG. 17.

The wireless communication interface 855 supports a cellularcommunication system such as LTE and LTE-Advanced, and provides wirelessconnection to a terminal located in a sector corresponding to the RRH860 via the RRH 860 and the antenna 840. The wireless communicationinterface 855 may typically include a BB processor 856 and the like. TheBB processor 856 is similar to the BB processor 826 described withreference to FIG. 17 except that the BB processor 856 is connected to anRF circuit 864 of the RRH 860 via the connection interface 857. Thewireless communication interface 855 may include a plurality of the BBprocessors 856, as illustrated in FIG. 18, and the plurality of BBprocessors 856 may, for example, correspond to a plurality of frequencybands used by the eNB 830 respectively. Note that, FIG. 18 illustratesan example in which the wireless communication interface 855 includesthe plurality of BB processors 856, but the wireless communicationinterface 855 may include the single BB processor 856.

The connection interface 857 is an interface for connecting the basestation apparatus 850 (wireless communication interface 855) to the RRH860. The connection interface 857 may be a communication module forcommunication on the high speed line which connects the base stationapparatus 850 (wireless communication interface 855) to the RRH 860.

Further, the RRH 860 includes a connection interface 861 and a wirelesscommunication interface 863.

The connection interface 861 is an interface for connecting the RRH 860(wireless communication interface 863) to the base station apparatus850. The connection interface 861 may be a communication module forcommunication on the high speed line.

The wireless communication interface 863 transmits and receives awireless signal via the antenna 840. The wireless communicationinterface 863 may typically include the RF circuit 864 and the like. TheRF circuit 864 may include a mixer, a filter, an amplifier and the like,and transmits and receives a wireless signal via the antenna 840. Thewireless communication interface 863 may include a plurality of the RFcircuits 864 as illustrated in FIG. 18, and the plurality of RF circuits864 may, for example, correspond to a plurality of antenna elements.Note that, FIG. 18 illustrates an example in which the wirelesscommunication interface 863 includes the plurality of RF circuits 864,but the wireless communication interface 863 may include the single RFcircuit 864.

In the eNB 830 illustrated in FIG. 18, one or more components includedin the processing unit 150 (the setting unit 151 and/or thecommunication control unit 153) described above with reference to FIG. 7may be mounted in the wireless communication interface 855 and/or thewireless communication interface 863. Alternatively, at least some ofthe components may be mounted in the controller 851. As an example, theeNB 830 may be equipped with a module including some or all componentsof the wireless communication interface 855 (for example, the BBprocessor 856) and/or the controller 851, and the above-described one ormore components may be mounted in the module. In this case, the modulemay store a program causing the processor to function as theabove-described one or more components (that is, a program causing theprocessor to perform the operation of the above-described one or morecomponents) and execute the program. As another example, the programcausing the processor to function as the above-described one or morecomponents may be installed in the eNB 830, and the wirelesscommunication interface 855 (for example, the BB processor 856) and/orthe controller 851 may execute the program. As described above, the eNB830, the base station apparatus 850, or the module may be provided as anapparatus including the above-described one or more components, and theprogram causing the processor to function as the above-described one ormore components may be provided. In addition, a readable recordingmedium in which the program is recorded may be provided.

In addition, for example, in the eNB 830 shown in FIG. 18, the wirelesscommunication unit 120 described with reference to FIG. 7 may beimplemented by the wireless communication interface 863 (for example,the RF circuit 864). Moreover, the antenna unit 110 may be implementedby the antenna 840. In addition, the network communication unit 130 maybe implemented by the controller 851 and/or the network interface 853.In addition, the storage unit 140 may be implemented by the memory 852.

5.2. Application Examples for Terminal Apparatus First ApplicationExample

FIG. 19 is a block diagram illustrating an example of a schematicconfiguration of a smartphone 900 to which the technology according tothe present disclosure may be applied. The smartphone 900 includes aprocessor 901, a memory 902, a storage 903, an external connectioninterface 904, a camera 906, a sensor 907, a microphone 908, an inputdevice 909, a display device 910, a speaker 911, a wirelesscommunication interface 912, one or more antenna switches 915, one ormore antennas 916, a bus 917, a battery 918, and a secondary controller919.

The processor 901 may be, for example, a CPU or a system on chip (SoC),and controls the functions of an application layer and other layers ofthe smartphone 900. The memory 902 includes a RAM and a ROM, and storesa program executed by the processor 901 and data. The storage 903 mayinclude a storage medium such as semiconductor memories and hard disks.The external connection interface 904 is an interface for connecting thesmartphone 900 to an externally attached device such as memory cards anduniversal serial bus (USB) devices.

The camera 906 includes an image sensor such as charge coupled devices(CCDs) and complementary metal oxide semiconductor (CMOS), and generatesa captured image. The sensor 907 may include a sensor group including,for example, a positioning sensor, a gyro sensor, a geomagnetic sensor,an acceleration sensor, and the like. The microphone 908 converts asound that is input into the smartphone 900 to an audio signal. Theinput device 909 includes, for example, a touch sensor which detectsthat a screen of the display device 910 is touched, a key pad, akeyboard, a button, a switch, or the like, and accepts an operation oran information input from a user. For example, the display device 910includes a screen such as liquid crystal displays (LCDs) and organiclight emitting diode (OLED) displays, and displays an output image ofthe smartphone 900. The speaker 911 converts the audio signal that isoutput from the smartphone 900 to a sound.

The wireless communication interface 912 supports a cellularcommunication system such as LTE or LTE-Advanced, and performs wirelesscommunication. The wireless communication interface 912 may typicallyinclude the BB processor 913, the RF circuit 914, and the like. The BBprocessor 913 may, for example, perform encoding/decoding,modulation/demodulation, multiplexing/demultiplexing, and the like, andperforms a variety of types of signal processing for wirelesscommunication. On the other hand, the RF circuit 914 may include amixer, a filter, an amplifier, and the like, and transmits and receivesa wireless signal via the antenna 916. The wireless communicationinterface 912 may be a one-chip module in which the BB processor 913 andthe RF circuit 914 are integrated. The wireless communication interface912 may include a plurality of BB processors 913 and a plurality of RFcircuits 914 as illustrated in FIG. 19. Note that, FIG. 19 illustratesan example in which the wireless communication interface 912 includes aplurality of BB processors 913 and a plurality of RF circuits 914, butthe wireless communication interface 912 may include a single BBprocessor 913 or a single RF circuit 914.

Further, the wireless communication interface 912 may support othertypes of wireless communication system such as a short range wirelesscommunication system, a near field communication system, and a wirelesslocal area network (LAN) system in addition to the cellularcommunication system, and in this case, the wireless communicationinterface 912 may include the BB processor 913 and the RF circuit 914for each wireless communication system.

Each antenna switch 915 switches a connection destination of the antenna916 among a plurality of circuits (for example, circuits for differentwireless communication systems) included in the wireless communicationinterface 912.

Each of the antennas 916 includes one or more antenna elements (forexample, a plurality of antenna elements constituting a MIMO antenna)and is used for transmission and reception of the wireless signal by thewireless communication interface 912. The smartphone 900 may include aplurality of antennas 916 as illustrated in FIG. 19. Note that, FIG. 19illustrates an example in which the smartphone 900 includes a pluralityof antennas 916, but the smartphone 900 may include a single antenna916.

Further, the smartphone 900 may include the antenna 916 for eachwireless communication system. In this case, the antenna switch 915 maybe omitted from a configuration of the smartphone 900.

The bus 917 connects the processor 901, the memory 902, the storage 903,the external connection interface 904, the camera 906, the sensor 907,the microphone 908, the input device 909, the display device 910, thespeaker 911, the wireless communication interface 912, and the secondarycontroller 919 to each other. The battery 918 supplies electric power toeach block of the smartphone 900 illustrated in FIG. 19 via a feederline that is partially illustrated in the figure as a dashed line. Thesecondary controller 919, for example, operates a minimally necessaryfunction of the smartphone 900 in a sleep mode.

In the smartphone 900 illustrated in FIG. 19, one or more componentsincluded in the processing unit 240 (the acquisition unit 241 and/or themeasurement unit 243) described above with reference to FIG. 8 may bemounted in the wireless communication interface 912. Alternatively, atleast some of the components may be mounted in the processor 901 or thesecondary controller 919. As an example, the smartphone 900 may beequipped with a module including some or all components of the wirelesscommunication interface 912 (for example, the BB processor 913), theprocessor 901, and/or the secondary controller 919, and theabove-described one or more components may be mounted in the module. Inthis case, the module may store a program causing the processor tofunction as the above-described one or more components (that is, aprogram causing the processor to perform the operation of theabove-described one or more components) and execute the program. Asanother example, the program causing the processor to function as theabove-described one or more components may be installed in thesmartphone 900, and the wireless communication interface 912 (forexample, the BB processor 913), the processor 901, and/or the secondarycontroller 919 may execute the program. As described above, thesmartphone 900 or the module may be provided as an apparatus includingthe above-described one or more components, and the program causing theprocessor to function as the above-described one or more components maybe provided. In addition, a readable recording medium in which theprogram is recorded may be provided.

In addition, for example, in the smartphone 900 shown in FIG. 19, thewireless communication unit 220 described with reference to FIG. 8 maybe implemented by the wireless communication interface 912 (for example,the RF circuit 914). Moreover, the antenna unit 210 may be implementedby the antenna 916. In addition, the storage unit 230 may be implementedby the memory 902.

Second Application Example

FIG. 20 is a block diagram illustrating an example of a schematicconfiguration of a car navigation apparatus 920 to which the technologyaccording to the present disclosure may be applied. The car navigationapparatus 920 includes a processor 921, a memory 922, a globalpositioning system (GPS) module 924, a sensor 925, a data interface 926,a content player 927, a storage medium interface 928, an input device929, a display device 930, a speaker 931, a wireless communicationinterface 933, one or more antenna switches 936, one or more antennas937, and a battery 938.

The processor 921 may be, for example, a CPU or a SoC, and controls thenavigation function and the other functions of the car navigationapparatus 920. The memory 922 includes a RAM and a ROM, and stores aprogram executed by the processor 921 and data.

The GPS module 924 uses a GPS signal received from a GPS satellite tomeasure the position (e.g. latitude, longitude, and altitude) of the carnavigation apparatus 920. The sensor 925 may include a sensor groupincluding, for example, a gyro sensor, a geomagnetic sensor, abarometric sensor, and the like. The data interface 926 is, for example,connected to an in-vehicle network 941 via a terminal that is notillustrated, and acquires data such as vehicle speed data generated onthe vehicle side.

The content player 927 reproduces content stored in a storage medium(e.g. CD or DVD) inserted into the storage medium interface 928. Theinput device 929 includes, for example, a touch sensor which detectsthat a screen of the display device 930 is touched, a button, a switch,or the like, and accepts operation or information input from a user. Thedisplay device 930 includes a screen such as LCDs and OLED displays, anddisplays an image of the navigation function or the reproduced content.The speaker 931 outputs a sound of the navigation function or thereproduced content.

The wireless communication interface 933 supports a cellularcommunication system such as LTE or LTE-Advanced, and performs wirelesscommunication. The wireless communication interface 933 may typicallyinclude the BB processor 934, the RF circuit 935, and the like. The BBprocessor 934 may, for example, perform encoding/decoding,modulation/demodulation, multiplexing/demultiplexing, and the like, andperforms a variety of types of signal processing for wirelesscommunication. On the other hand, the RF circuit 935 may include amixer, a filter, an amplifier, and the like, and transmits and receivesa wireless signal via the antenna 937. The wireless communicationinterface 933 may be a one-chip module in which the BB processor 934 andthe RF circuit 935 are integrated. The wireless communication interface933 may include a plurality of BB processors 934 and a plurality of RFcircuits 935 as illustrated in FIG. 20. Note that, FIG. 20 illustratesan example in which the wireless communication interface 933 includes aplurality of BB processors 934 and a plurality of RF circuits 935, butthe wireless communication interface 933 may be a single BB processor934 or a single RF circuit 935.

Further, the wireless communication interface 933 may support othertypes of wireless communication system such as a short range wirelesscommunication system, a near field communication system, and a wirelessLAN system in addition to the cellular communication system, and in thiscase, the wireless communication interface 933 may include the BBprocessor 934 and the RF circuit 935 for each wireless communicationsystem.

Each antenna switch 936 switches a connection destination of the antenna937 among a plurality of circuits (for example, circuits for differentwireless communication systems) included in the wireless communicationinterface 933.

Each of the antennas 937 includes one or more antenna elements (forexample, a plurality of antenna elements constituting a MIMO antenna)and is used for transmission and reception of the wireless signal by thewireless communication interface 933. The car navigation apparatus 920includes a plurality of antennas 937 as illustrated in FIG. 20. Notethat, FIG. 20 illustrates an example in which the car navigationapparatus 920 includes a plurality of antennas 937, but the carnavigation apparatus 920 may include a single antenna 937.

Further, the car navigation apparatus 920 may include the antenna 937for each wireless communication system. In this case, the antenna switch936 may be omitted from a configuration of the car navigation apparatus920.

The battery 950 supplies electric power to each block of the carnavigation apparatus 920 illustrated in FIG. 20 via a feeder line thatis partially illustrated in the figure as a dashed line. In addition,the battery 950 accumulates the electric power supplied from thevehicle.

In the car navigation apparatus 920 illustrated in FIG. 20, one or morecomponents included in the processing unit 240 (the acquisition unit 241and/or the measurement unit 243) described above with reference to FIG.8 may be mounted in the wireless communication interface 933.Alternatively, at least some of the components may be mounted in theprocessor 921. As an example, the car navigation apparatus 920 may beequipped with a module including some or all components of the wirelesscommunication interface 933 (for example, the BB processor 934), and theabove-described one or more components may be mounted in the module. Inthis case, the module may store a program causing the processor tofunction as the above-described one or more components (that is, aprogram causing the processor to perform the operation of theabove-described one or more components) and execute the program. Asanother example, the program causing the processor to function as theabove-described one or more components may be installed in the carnavigation apparatus 920, and the wireless communication interface 933(for example, the BB processor 934) and/or the processor 921 may executethe program. As described above, the car navigation apparatus 920 or themodule may be provided as an apparatus including the above-described oneor more components, and the program causing the processor to function asthe above-described one or more components may be provided. In addition,a readable recording medium in which the program is recorded may beprovided.

In addition, for example, in the car navigation apparatus 920 shown inFIG. 20, the wireless communication unit 220 described with reference toFIG. 8 may be implemented by the wireless communication interface 933(for example, the RF circuit 935). Moreover, the antenna unit 210 may beimplemented by the antenna 937. In addition, the storage unit 230 may beimplemented by the memory 922.

In addition, the technology of the present disclosure may also berealized as an in-vehicle system (or a vehicle) 940 including one ormore blocks of the car navigation apparatus 920, the in-vehicle network941, and a vehicle module 942. In other words, the in-vehicle system (ora vehicle) 940 may be provided as a device which includes theacquisition unit 241 and the measurement unit 243. The vehicle module942 generates vehicle data such as vehicle speed, engine speed, andtrouble information, and outputs the generated data to the in-vehiclenetwork 941.

6. Conclusion

The embodiment of the present disclosure has been described above indetail with reference to FIGS. 1 to 20. As described above, the terminalapparatus feeds back the CQI of the serving base station, which has beencalculated on the basis of the results of measuring the referencesignals received from the serving base station and the neighbor basestation and the information related to Pc of the neighbor base station.In this manner, it becomes possible to feed back the CQI inconsideration of the difference in the received power between thereference signal and the data signal related to the CSI-RS from theneighbor base station and to perform selection and the like of a moreappropriate modulation scheme by the serving base station.

The preferred embodiment(s) of the present disclosure has/have beendescribed above with reference to the accompanying drawings, whilst thepresent disclosure is not limited to the above examples. A personskilled in the art may find various alterations and modifications withinthe scope of the appended claims, and it should be understood that theywill naturally come under the technical scope of the present disclosure.

For example, the technical features that have been described in therespective embodiments described above can be appropriately combined.

In addition, the processing described by using the flowcharts and thesequence diagrams in this specification may not necessarily executed inthe orders described in the drawings. Some processing steps may beexecuted in parallel. In addition, additional processing steps may beemployed, and a part of the processing steps may be omitted.

Further, the effects described in this specification are merelyillustrative or exemplified effects, and are not limitative. That is,with or in the place of the above effects, the technology according tothe present disclosure may achieve other effects that are clear to thoseskilled in the art from the description of this specification.

Additionally, the present technology may also be configured as below.

(1)

An apparatus including:

a processing unit that feeds back a channel quality indicator (CQI) of aserving base station, which is calculated on a basis of results ofmeasuring reference signals received from the serving base station and aneighbor base station and information related to a power differencebetween the reference signal and a data signal of the neighbor basestation, to the serving base station.

(2)

The apparatus according to (1),

in which the information related to the difference includes informationrelated to an assumed ratio of an energy per resource element (EPRE) ofthe data signal with respect to an EPRE of the reference signal of theneighbor base station.

(3)

The apparatus according to (2),

in which the information related to the difference includes informationthat indicates the ratio corresponding to at least a part of aninterference measurement resource (IMR), and

the reference signal of the neighbor base station is received by the IMRcorresponding to the ratio of the reference signal.

(4)

The apparatus according to (3),

in which one or more reference signals are received by the IMR.

(5)

The apparatus according to any one of (1) to (4),

in which the information related to the difference includes informationthat indicates a base station corresponding to each IMR, and

the reference signal of the neighbor base station is received by adifferent IMR for each base station.

(6)

The apparatus according to any one of (1) to (5),

in which the information related to the difference includes informationthat indicates restriction of a transmission schedule of the data signalin the neighbor base station in a predetermined period of time infuture.

(7)

The apparatus according to (6),

in which the information that indicates the restriction of thetransmission schedule includes information that indicates whether or noteach sub-band is used to transmit the data signal.

(8)

The apparatus according to (6) or (7),

in which the information that indicates the restriction of thetransmission schedule includes information that indicates whether or noteach beam is used to transmit the data signal.

(9)

The apparatus according to any one of (6) to (8),

in which the information related to the difference includes informationthat indicates the restriction of the transmission schedulecorresponding to each IMR, and

the reference signal of the neighbor base station is received by an IMRcorresponding to the restriction of the transmission schedule of theneighbor base station.

(10)

The apparatus according to any one of (1) to (9),

in which the reference signal is a channel state information referencesignal (CSI-RS).

(11)

The apparatus according to any one of (1) to (10),

in which the data signal is a signal that is transmitted through aphysical downlink shared channel (PDSCH).

(12)

The apparatus according to any one of (1) to (11),

in which the reference signal is subjected to beamforming.

(13)

An apparatus including:

a processing unit that provides a notification of information related toa power difference between a reference signal and a data signal of aneighbor base station to a terminal apparatus under the control of theapparatus and receives feedback of a CQI that is calculated on a basisof results of measuring reference signals that are received from aserving base station and the neighbor base station and informationrelated to the difference from the terminal apparatus.

(14)

The apparatus according to (13),

in which the processing unit provides a notification of information thatindicates an assumed ratio of an EPRE of the data signal with respect toan EPRE of the reference signal, which corresponds to each IMR, to theneighbor base station.

(15)

The apparatus according to (14),

in which the processing unit provides a notification of information thatindicates a position of the IMR to the neighbor base station.

(16)

The apparatus according to any of (13) to (15),

in which the processing unit acquires information related to atransmission schedule of the reference signal from the neighbor basestation.

(17)

The apparatus according to (16),

in which the processing unit acquires information that indicates anassumed ratio of the EPRE of the data signal with respect to the EPRE ofthe reference signal of the neighbor base station.

(18)

The apparatus according to any one of (13) to (17),

in which the processing unit controls whether or not to provide thenotification of the information related to the difference to theterminal apparatus.

(19)

The apparatus according to any one of (13) to (18),

in which the processing unit acquires information that indicatesrestriction of a transmission schedule of the data signal in theneighbor base station in a predetermined period of time in future fromthe neighbor base station.

(20)

A method including:

feeding back a channel quality indicator (CQI) of a serving basestation, which is calculated on a basis of results of measuringreference signals received from the serving base station and a neighborbase station and information related to a power difference between thereference signal and a data signal of the neighbor base station, to theserving base station.

(21)

A method including:

providing, by a processor, a notification of information related to apower difference between a reference signal and a data signal of aneighbor base station to a terminal apparatus under the control of theapparatus and receiving feedback of a CQI that is calculated on a basisof results of measuring reference signals that are received from aserving base station and the neighbor base station and informationrelated to the difference from the terminal apparatus.

(22)

A program causing a computer to function as:

a processing unit that feeds back a channel quality indicator (CQI) of aserving base station, which is calculated on a basis of results ofmeasuring reference signals received from the serving base station and aneighbor base station and information related to a power differencebetween the reference signal and a data signal of the neighbor basestation, to the serving base station.

(23)

A program causing a computer to function as:

an apparatus including:

-   -   a processing unit that provides a notification of information        related to a power difference between a reference signal and a        data signal of a neighbor base station to a terminal apparatus        under the control of the apparatus and receives feedback of a        CQI that is calculated on a basis of results of measuring        reference signals that are received from a serving base station        and the neighbor base station and information related to the        difference from the terminal apparatus.

REFERENCE SIGNS LIST

-   1 system-   100 base station-   110 antenna unit-   120 wireless communication unit-   130 network communication unit-   140 storage unit-   150 processing unit-   151 setting unit-   153 communication control unit-   200 terminal apparatus-   210 antenna unit-   220 wireless communication unit-   230 storage unit-   240 processing unit-   241 acquisition unit-   243 measurement unit-   300 neighbor base station

The invention claimed is:
 1. An apparatus comprising: a processingcircuit that feeds back a channel quality indicator (CQI) of a servingbase station, which is calculated on a basis of an estimated receivedpower of a desired data signal estimated from a result of measuring afirst reference signal received from the serving base station, anestimated received power of an interference data signal estimated from aresult of measuring a second reference signal received from a neighborbase station, and information related to a power difference between thefirst reference signal and a data signal of the neighbor base station,to the serving base station.
 2. The apparatus according to claim 1,wherein the information related to the difference includes informationrelated to an assumed ratio of an energy per resource element (EPRE) ofthe data signal with respect to an EPRE of the second reference signalof the neighbor base station.
 3. The apparatus according to claim 2,wherein the information related to the difference includes informationthat indicates the ratio corresponding to at least a part of aninterference measurement resource (IMR), and the second reference signalof the neighbor base station is received by the IMR corresponding to theratio.
 4. The apparatus according to claim 3, wherein one or morereference signals are received by the IMR.
 5. The apparatus according toclaim 1, wherein the information related to the difference includesinformation that indicates a base station corresponding to each IMR, andthe second reference signal of the neighbor base station is received bya different IMR for each base station.
 6. The apparatus according toclaim 1, wherein the information related to the difference includesinformation that indicates restriction of a transmission schedule of thedata signal in the neighbor base station in a predetermined period oftime in future.
 7. The apparatus according to claim 6, wherein theinformation that indicates the restriction of the transmission scheduleincludes information that indicates whether or not each sub-band is usedto transmit the data signal.
 8. The apparatus according to claim 6,wherein the information that indicates the restriction of thetransmission schedule includes information that indicates whether or noteach beam is used to transmit the data signal.
 9. The apparatusaccording to claim 6, wherein the information related to the differenceincludes information that indicates the restriction of the transmissionschedule corresponding to each IMR, and the second reference signal ofthe neighbor base station is received by an IMR corresponding to therestriction of the transmission schedule of the neighbor base station.10. The apparatus according to claim 1, wherein the first and secondreference signals are channel state information reference signals(CSI-RS).
 11. The apparatus according to claim 1, wherein the datasignal is a signal that is transmitted through a physical downlinkshared channel (PDSCH).
 12. The apparatus according to claim 1, whereinthe first and second reference signals are subjected to beamforming. 13.An apparatus comprising: a processing circuit that provides anotification of information related to a power difference between afirst reference signal and a data signal of a neighbor base station to aterminal apparatus under the control of the apparatus and receivesfeedback of a CQI that is calculated on a basis of an estimated receivedpower of a desired data signal estimated from a result of measuring thefirst reference signal that is received from a serving base station, anestimated received power of an interference data signal estimated from aresult of measuring a second reference signal received from the neighborbase station, and information related to the difference from theterminal apparatus.
 14. The apparatus according to claim 13, wherein theprocessing circuit provides a notification of information that indicatesan assumed ratio of an EPRE of the data signal with respect to an EPREof the reference signal, which corresponds to each IMR, to the neighborbase station.
 15. The apparatus according to claim 14, wherein theprocessing circuit provides a notification of information that indicatesa position of the IMR to the neighbor base station.
 16. The apparatusaccording to claim 13, wherein the processing circuit acquiresinformation related to a transmission schedule of the second referencesignal from the neighbor base station.
 17. The apparatus according toclaim 16, wherein the processing circuit acquires information thatindicates an assumed ratio of the EPRE of the data signal with respectto the EPRE of the second reference signal of the neighbor base station.18. The apparatus according to claim 13, wherein the processing circuitcontrols whether or not to provide the notification of the informationrelated to the difference to the terminal apparatus.
 19. The apparatusaccording to claim 13, wherein the processing circuit acquiresinformation that indicates restriction of a transmission schedule of thedata signal in the neighbor base station in a predetermined period oftime in future from the neighbor base station.
 20. A method comprising:feeding back a channel quality indicator (CQI) of a serving basestation, which is calculated on a basis of an estimated received powerof a desired data signal estimated from a result of measuring a firstreference signal received from the serving base station, an estimatedreceived power of an interference data signal estimated from a result ofmeasuring a second reference signal received from a neighbor basestation, and information related to a power difference between the firstreference signal and a data signal of the neighbor base station, to theserving base station.